The present grant proposes to use cloned primed lymphocyte typing (PLT) reagents to identify determinants of the HLA-D region which may show closer associations with insulin-dependent diabetes (IDD) and rheumatoid arthritis (RA) than do the HLA-DR and -Dw specificities defined by current typing methods. Our studies suggest that in IDD patients, there are differences in the frequencies of Dw specificites, as compared to those in normals, that are not simply a correlate of the well-documented differences in frequencies of DR specificities between patients and normals. The cloned PLT method offers a means for more precise definition of individual D-region determinants and therefore, potentially, for more exact identification of disease-associated determinants than that provided by Dw and DR typing. We shall prepare cloned PLT reagents against DR4-positive and DR2-positive haplotypes of Caucasian IDD and rheumatoid arthritis patients (DR4 and DR2 are, respectively, positively and negatively associated with these two diseases). These reagents will be screened on panels of cells of patients and normals in an attempt to identify those recognizing determinants highly associated with the disease in question. If such reagents are found, they will then be tested on panels of cells of Japanese (as the Dw associations with IDD in this population are different from those in Caucasians) and Black patients with the disease in question, to determine whether the "disease-related" determinants of Caucasians are also found in these populations. The reagents will also be cross-tested, e.g. reagents identifying IDD-associated determinants will be tested on panels of cells of patients with rheumatoid arthritis.